The Doctor looks and seems human. He's handsome, witty, and could be mistaken for just another man in the street. But he is a Time Lord: a 900 year old alien with 2 hearts, part of a gifted civilization who mastered time travel. The Doctor saves planets for a living – more of a hobby actually, and he's very, very good at it. He's saved us from alien menaces and evil from before time began – but just who is he?

Trainee doctor Martha Jones has her hands full balancing her medical studies with placating her demanding family. So the last thing she needs is to find that the hospital where she works has been transported to the moon, where it's invaded by an overbearing alien police force. There she encounters a patient called John Smith, who seems curiously at ease with the situation…

Martha takes her first trip in the Tardis, all the way back to Elizabethan England. She and the Doctor hear of a series of bizarre deaths and discover that playwright William Shakespeare is being controlled by dangerous witch-like creatures. It seems the time-travelling duo must defeat ancient forces to prevent history from being rewritten.

The Doctor investigates disappearances in New York at the height of the depression in the 1930s. Nefarious Pig Men linger in the sewers and the Daleks prepare an audacious plan at the top of the Empire State Building

The newly-created Dalek-human hybrid, and the other three members of the Cult of Skaro launch an attack on Hooverville, along with their Pig Slaves. The Doctor, Martha, and Frank manage to escape, but discover that the Daleks' plan involving the Empire State Building...

In a far-flung galaxy, saboteurs are at work, and crew members are being possessed. The TARDIS crew find themselves in the 42nd century on a spaceship, SS Pentallian, slowly being pulled into a sun, and must find a way to survive

After being brought back to life in The Parting of the Ways, Captain Jack Harkness was just left on the Gamestation by the Doctor and Rose. In this episode, Captain Jack Harkness storms back into the Doctor's life, and the TARDIS is thrown to the end of the universe itself.

Harry Saxon becomes Prime Minister and his reign of terror begins – but that's only the start of his ambitions, as he announces mankind's first contact with an alien race, the Toclafane. An audacious plan spanning the whole of time and space begins to close around the Earth, in the penultimate episode of Russell T Davies's Doctor Who.

One year has passed since the events of "The Sound of Drums." The Earth has been conquered and its population enslaved, the Doctor is the Master's prisoner, and the warships of a new Time Lord Empire rise from the ashes. The fate of the world is in Martha Jones' hands.